The refinement of the bovine proteolytic enzyme gamma-chymotrypsin at 1.9 Angstrom resolution has been completed. The aspartic protease from Rhizopus chinensis has been subjected to further high resolution data collection. A mechanism for the inhibition of the enzyme by pepstatin has been proposed. Pepstatin inhibited protein has been crystallized. The enzyme S-adenosyl methionine synthetase has been crystallized in several crystal forms that show promise of being amenable to X-ray diffraction analysis.